package bishi.day35_6_3;

import java.util.*;
/**
 * 年会抽奖
 * 动态规划
 * @author 是阿秋啊
 * @date 2022/06/04 14:07
 **/
public class chou_jiang {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) {
            int n = sc.nextInt();
            double ret = (double) helper(n)/count(n)*100;
            System.out.printf("%2.2f%%\n",ret);
        }
    }

    private static double count(int n) {
        double sum = 1;
        for (int i = 2; i <= n; i++) {
            sum*=i;
        }
        return sum;
    }

    private static long helper(int n) {
        if(n == 1) {
            return 0;
        }
        if (n == 2) {
            return 1;
        }
        return (n - 1)*(helper(n - 1) + helper(n - 2));
    }
}